The present invention relates generally to belt presses used for increasing the solids concentration of slurries by reducing the liquid component, and more particularly to an improved frame for such a belt press which permits the removal and/or installation of endless belts.
Belt presses have been known for many years and have been used in many applications, such as the dewatering of sewage sludge, peat, industrial wastes, cement slurries, and coal slurries. The belt press of the present invention was designed to handle large volumes of slurry containing a wide variety of solids, including coarse, abrasive, relatively incompressible materials, such as coal fines or tailings which are washed from coal after it has been crushed.
Belt presses commonly consist of a pair of foraminous or water permeable belts which are held taught in two separate loops by a series of parallel support rolls mounted in a rigid frame. The loops are arranged so that the belts travel together but with a narrow gap between them in a serpentine path over special squeezing rolls. The material to be dewatered is forced into the narrow inter belt gap where the squeeze rolls exert pressure on the belt-slurry-belt sandwich to force water out through the porous belts.
In the past, such presses used belts which were threaded into place and spliced together. Spliced belts proved vulnerable to misalignment on the rolls and to frequent splitting along the spliced seam due to the extreme tension under which they operate.
The substitution of endless belts in belt presses has significantly improved the operation of the press and the life of the belts. Endless belts are not subject to the substantial stress along seams which was a major source of belt press down time when spliced belts were used. However, even endless belts must be periodically replaced due to their tendency to stretch or wear with time.
The use of endless belts requires a special frame for the press; in particular, one that can be separated or disassembled to permit belt replacement. Such frame designs have heretofore proven unsatisfactory because they have required either excessive time, care or equipment when making a belt change. Among their shortcomings is the problem that if the frame is not opened far enough, it is impossible to remove the belt. On the other hand, if the frame is opened too far, it may break or become deformed due to excessive stresses on the frame members.
Also, the separable frame sections are typically held in place by a number of large bolts which must be loosened and removed before the frame section can be separated. In some frame designs, the frame is provided with removable spacers which are also held in place with large bolts. The loosening and removal of bolts of this magnitude (typically 11/4 inches in diameter) is a tedious step which adds to the delay in the belt replacement process.
Prior art endless belt presses use one of two systems for breaking the press open and replacing the belts. In the first, known as the "outrigger method", telescoping members are extended laterally from the side of the press to provide stability. When the outriggers reach full extension, they are raised by jacks to effect the lifting of certain upper frame sections to separate the frame and permit replacement of an endless belt.
A major disadvantage of the outrigger method is the cost of constructing outriggers strong enough to support massive belt presses yet mobile enough to be easily extended by workmen or equipment at the job site. Furthermore, because of deflections in the telescoping members, it is difficult to predict or calculate the stresses within the frame itself, which may lead to overdesigning to be on the safe side.
An additional disadvantage of the outrigger method is that when jacks are used to raise the belt press frame to allow extraction of the removable frame sections, there is a hazard of jacking the "belt change" side of the frame too high relative to the opposite side of the frame, which may cause the frame to become severely misaligned or even cracked.
The second system used to open belt presses for belt replacement is to substitute a crane for outriggers and jacks to lift the entire top of the frame or at least the "belt change" side of the frame. Although this method eliminates the costly and cumbersome outriggers, it is less precise and consequently more prone to "springing" or cracking the press frame.
The crane method also requires the time consuming removal and replacement of numerous large bolts which hold the frame sections together.
Accordingly, it is a principal object of the present invention to provide a frame for a belt press which permits the replacement of endless belts safely, in a minimum amount of time, with minimal cost, and with maximum accuracy.
Another object of the invention is to provide a belt press having a frame which has removable sections on one side and internally positionable jack means to facilitate rapid and easy removal and replacement of the endless belts through said one side.
Another object of the present invention is to provide a frame for a press frame in which at least one side of the frame is hinged so that belt replacement can be effected through the other side with a minimum risk of the frame cracking, deforming or springing.
Another object of the invention is to provide a belt press frame which is openable to permit replacement of the endless belts wherein all of the loading to effect the opening of the frame is confined within the frame structure itself.
A further object of this invention is to provide a frame for a belt press which can be opened to permit the lateral removal and replacement of an endless belt with a minimum number of large bolts or other fastening devices which have to be removed or loosened.